In esters of chrysanthemumic acid which are known as insecticides, various kinds of alcohol components have been studied, and the esters employing such alcohols have been put to practical use. These crysanthemumic esters are, however, liable to be decomposed through oxidation upon exposure to light, and their outdoor use is, therefore, limited. Much recent research has been directed to the acid components of those esters. As a result, there are known compounds which are more stable against light than pyrethroid, for example, esters of dihalovinylcrysanthemumic acid of the formula (X) with halogen atoms substituted for methyl groups: ##STR3## in which X stands for a halogen atom, and esters of tetramethylcyclopropanecarboxylic acid of the formula XI: ##STR4##
The esters of the acid represented by the formula XI have difficulties unsolved in practical use, since it is inferior in insecticidal activity to the esters of chrysanthemumic acid or those of the acids of the formula X, and higher in toxicity to men and cattle. The esters of the acids of the formula X are not always acceptable, either, in view of the problems of environmental pollution, chromic toxicity, etc.
As a result of strenuous researches, the inventors of this invention have discovered that if some of its methyl groups are replaced by halogen atoms or halomethyl groups, the esters of the acid represented by the formula XI surprisingly have remarkably improved insecticidal activities and largely reduced toxicities. The esters of the novel cyclopropanecarboxylic acids compared with the esters of the non-replaced acid exhibit far higher stabilities against light than the known chrysanthemumic acid esters.
The present invention has been accomplished on the basis of the above-mentioned knowledge.